Motion picture print films, the film that is shown in movie theaters, commonly employ optical soundtracks along at least one edge of the film. The most common optical soundtracks presently in use are analog soundtracks of the "variable area" type wherein signals are recorded in the form of a varying ratio of opaque to relatively clear area along the soundtrack. During projection of the motion picture images, a light source illuminates the soundtrack and a photosensor senses the light passing through and modulated by the soundtrack to produce an audio signal that is sent to amplifiers of the theater sound system. Digital soundtracks for motion picture films have been more recently introduced, wherein sound information is recorded in a digital format, e.g. comprising small data bit patterns on the film, typically between perforations of the motion picture film (e.g., Dolby.TM. Digital Stereo soundtracks) or along the film edge (e.g., Sony.TM. Dynamic Digital Sound soundtracks). U.S. Pat. Nos. 4,600,280 and 4,461,552, e.g., disclose methods in which digital audio is photographically recorded on motion picture film.
In order to optimize the visual quality of the motion picture image as well as the sound quality of the soundtrack recorded on a motion picture print film, the motion picture and soundtrack are first typically captured or recorded on separate photosensitive films as negative images, and the resulting negatives are then printed in synchronization on a motion picture print film to form positive images. On account of the very short exposure times which must be given to each separate picture, or frame, in capturing a motion picture image, a camera negative film employing relatively fast silver halide emulsions is typically used to record the motion picture images (e.g., Eastman Color Negative Films). In order to reproduce the wide ranges of colors and tones which may be found in various images, the camera film typically also has a relatively low contrast or gamma. Variable area analog soundtracks and digital soundtracks, however, are best recorded with high contrast, relatively slower speed films (e.g., Eastman Sound Recording Films) in order to generate desired sharp images for the sound recording and minimize background noise generated by relatively high minimum densities typically associated with relatively fast camera negative films.
Sound recording films have typically comprised silver-based black-and-white films free from any dye-forming coupler compounds, designed to be processed with conventional black-and-white developer solutions to form silver-based black-and-white images, such as the D-97 process as specified in Module 15 of the Kodak Publication H-24 titled "Manual for Processing Eastman Motion Picture Film", the disclosure of which is incorporated herein by reference. In such processes, after exposure, black-and-white images are generally produced by developing silver halide in a black-and-white developer, such as hydroquinone, to form a silver image by reducing the exposed silver halide to silver metal. The undeveloped silver halide is removed from the film by "fixing" with aqueous sodium thiosulfate. The silver metal remaining in the print represents the image.
Most motion picture scenes today are filmed using color negative film designed to be processed in a color developer process wherein dye images are formed and essentially all silver is removed, such as the process ECN-2, described in Module 7 of the Kodak Publication H-24 incorporated by reference above. Motion picture film processing laboratories which wish to process both black-and-white sound recording film and color negative films must have separate processing systems; one for color and one for black-and-white, as the two systems are not compatible. Various photographic products have been previously proposed for forming black-and-white images through use of color processing, such as U.S. Pat. Nos. 5,362,616 and 5,491,053 directed towards chromogenic black-and-white photographic elements for forming neutral images. While U.S. Pat. No. 5,491,053 is directed towards chromogenic black-and-white motion picture print films, and U.S. Pat. No. 5,362,616 suggests the technology disclosed therein may be advantageously used to produce a motion picture sound track film, the photographic materials described in these patents require specific emulsion layer formats and cyan, magenta, and yellow dye-forming coupler combinations in order to form neutral images, and such films do not necessarily meet desired performance criteria for sound recording films. It would, therefore, be advantageous to provide an effective sound recording film which could be utilized with a conventional color processing system. It would be further advantageous to be able to provide such a film at low costs and high quality.